Modern communication systems are based on a number of key technologies (a) wireless systems such as Wi-Fi—which relies on RF electromagnetic fields for wireless communication of data over relatively short distances, (b) optical communication where light travelling through optical fibers conveys information, often over very long distances, and/or (c) optical communication where light travelling through free-space conveys information over a short distance (e.g., Radio-over-Free-Space (RoFS) including Light-Fidelity (Li-Fi)). RF-based communication is a vital part of modern communications, enabling compact, portable, and smart telecommunication devices to exchange data and the Internet of Things (IoT). However, these RF-based systems have a relatively short range (typically up to 100 meters). Optical communication, on the other hand, can have a very large range (thousands of kilometres).
Devices that link RF data to optical data therefore constitute an extremely valuable emergent technology. Radio-over-Fiber or Radio-Frequency-over-Fiber (hereinafter referred to as RoF) devices typically allow conversion of RF signals to the optical domain and further transmission via optical fibers. Conventional RoF devices, as shown in FIG. 1, include a signal source, an RF-to-optical encoder, a fiber-optic link, a photodetection unit and demodulation electronics. In these systems, RF-to-optical encoding is traditionally achieved by either (i) intensity modulation of a laser source via, e.g., controlling laser current, or (ii) intensity/phase modulation of light using electro-optical crystals, both using guided RF signals. This requires direct electrical connection and complex amplification and filtering stages. Efficient conversion of microwave signals into an optical signal is therefore an outstanding challenge due to small Kerr nonlinearities of conventional crystals, often necessitating high optical pump power. This renders high modulation-depth and efficient optical encoding of RF signals a difficult task.
There is therefore a need for improved data communications system architectures and/or an improved optical antenna that will enable direct encoding of free-space RF signals into the optical domain and eliminate the need for any electrical contacts at the receiver end, or at least a need for a useful alternative.